FK 506 is an experimental immunosuppressive drug that has been used with encouraging results as primary therapy in early clinical trials of renal transplantation.1,2 In an early randomized trial comparing FK 506 and cyclosporine (CyA)-based immunosuppression, the major advantage of FK 506 appeared to be the ability to taper steroids, permitting FK 506 monotherapy, with no additional risk of rejection episodes in 60% of patients.2 This is usually not possible with CyA-based immunosuppression because of both increased risk of rejection and nephrotoxicity.3 The superior results observed with FK 506 may be due in part to its greater immunosuppressive potency compared to Cy A.4 These observations led us to evaluate FK 506 as a salvage agent to “rescue” renal allografts failing CyA-based therapy. We previously reported that FK 506 is unlikely to salvage renal allografts with chronic rejection or CyA toxicity.5 However, conversion from CyA to FK 506 in failing grafts with ongoing acute rejection appeared to be much more promising, with graft salvage in 17 of 24 (71%) such cases.5 We report herein our expanded experience with FK 506 conversion as “rescue” therapy for renal allografts with ongoing rejection failing CyA therapy.